Plating hanger for obtaining homogeneous plating

ABSTRACT

A plating hanger is provided. The plating hanger provides a homogeneous plating by equalizing high current and low current zones by changing distances of part connections holding materials to be coated to an anode. The plating hanger includes at least one hanger frame, and a hanger body having part connections holding the materials to be coated on the plating hanger

CROSS REFERENCE TO THE RELATED APPLICATIONS

This application is the national stage entry of International Application No. PCT/TR2019/050874, filed on Oct. 16, 2019, which is based upon and claims priority to Turkish Patent Application No. 2018/17664 filed on Nov. 22, 2018, the entire contents of which are incorporated herein by reference.

TECHNICAL FIELD

The invention relates to plating hangers used for plating (electroplating) parts in Galvano industry. In particular, the invention relates to a plating hanger which provides a homogeneous plating with the equalization of the high current and low current zones by changing the distances of the part connections holding the part thereon to the anode.

BACKGROUND

The first experiments of what we know today as electro-plating were carried out in 1805 by the well-known Italian chemist, Luigi Brugnatelli. He used the recently discovered electric battery in the gold plating process. The process was developed by John Wright, who uses potassium cyanide, a more useful electrolyte for gold and silver plating , while at the same time providing good adhesion and plating thickness. Until the middle of the 19th century, electro-depositing was the main field of application for the polishing of jewelery and decorative items (Endres, MacFarlane, and Abbott, 2007).

Boettper made the first nickel plating, the bath composition being nickel sulfate and ammonium sulfate. In 1849, nickel plating commenced in the commercial sense for the first time (Berk, 2004). In parallel to the developments in electrochemistry in the 1850s, the use of metals such as zinc, nickel, tin and brass began to spread. At the beginning of the 20th century, the applications made to the parts used in the electronics industry were manifested by the chemistry of the plating solution and the developments in the material. Later, during the war years, there was also an increase in gold plating for electronic components. Less harmful plating solutions have begun to be used. This trend continued with the increase in the control of materials harmful to the environment. Developing solution composition and power supply technology have led to the proliferation and rapid development of applications in the plating field. Alternative research for metals such as chromium, nickel and cadmium has continued. Anti-corrosion and abrasion resistant platings have started to have a superior market in the electroplating sector (Endres et al., 2007). Commercially depositable metals are; Cr, Ni, Au, Ag, Zn, Cd, Cu and various alloys (Zn-Ni, Zn-Co, Zn-Fe etc.) platings. The production area of the entire electroplating industry is based on aqueous solutions.

The needs arising in parallel to the development of plastic technology and the widespread use of plastic materials have led to the process of metal plating on plastic. Nowadays plastic plating is widely applied in almost every sector (automotive, white goods, sanitary ware, armature, cosmetics, textile, furniture, etc.). The plastic has become indispensable for plating as it can be processed easily, as compared to the high costs of its rivals, i.e. the metals such as zamak, yellow casting, and aluminium. With the increasing use of plastic in every field of industry, chrome plating on plastic comes to the forefront. The chrome plating process on plastic adds an additional visuality to the plated product, but the longevity of the plated material is one of the main reasons for this plating process.

For these reasons, the design of the plating hangers used in the chrome plating process on the plastic material is an important factor in the homogeneity of the plating. Electrolytic plating is a process of depositing metal from a chemical medium to a material surface with the help of electrical energy. The plating bath is a solution containing dissolved metal salt or compound. In addition to the dissolved metal salt or compound which conducts the electricity, there are two electrodes, anode and cathode, for conducting electrical energy to the solution. Here, the anode is the coating material, ie the wearing side, and the electrode connected to the positive (+) pole of the energy source. On the other hand, the cathode is the coated side, ie the coated material, and is connected to the negative (−) pole of the energy source. In the above-mentioned basic principle of the plating, the distance to the anode and the current density are two important variables for the homogeneity of the plating. Knowing the current density is very important because it affects the amount and property of the plating taking place at the cathode. What is important in the plating is the ampere size applied per decimeter square (A/dm²). The division of the amperage into the surface area is expressed as the current density. In the plating, the calculations are made with the surface area. Assuming that the current value applied to one of the two equal parts having the same surface area is twice the current applied to the other, a double metal is plated on the surface of the part, on which the high current value is applied, compared to the other. In this sense, the greatest factor in the emergence of the plating hanger according to the invention is the need to provide a homogeneous plating by eliminating the excess current density formed on the materials to be coated. In all of the R&D studies, current maps were prepared by using analysis programs, and after these programmatic experiments and applications, the necessity of redesigning the plating hanger emerged.

In the state of the art, there are known patent applications for the electroplating process and apparatus used in this process. In particular, patent applications relating to hangers used in said plating process can be cited as evidence of the importance of this subject. For example, the application of LINHAI WEIXING ELECTROPLATING CO LTD, CN207608651 discloses a novelty in the plating hanger. In another Chinese application (CN207391591), further improvements to the plating hanger are described. The plating hangers used in the present art are generally designed in such a way that their parts are at equal distances to the anode in the flat frame. Therefore, the parts in the central region of the hanger are less coated because they remain in the low current zone, while the edge regions have more plating thickness because they remain in the high current zone. Also in the present art, the current connection points of the hanger cause the parts in the hanger corner/edge regions to be coated more because the current prefer the shortest path in the current distribution. However, since the skeletons of the prior art hangers are designed in the bridge structure, low and high current zones are formed because the current prefers the shortest path.

In case that the patent applications and the some practices in the prior art, which are only given above as example, as well as all the literature and patent applications are examined, there has not been found a plating hanger, as described in details below, for homogeneously plating the material to be coated.

SUMMARY

In order to overcome the disadvantages of the applications in the prior art, the object of the invention is to provide a plating hanger for obtaining a homogeneous plating. Another object of the invention is to produce the parts coated having more homogeneous thickness on the hanger. For this purpose, the design of the hanger connection body (hanger head) was changed in the first stage. In the designs of the previous hanger connection body, the outer frame of the hanger constitutes the high current zone, and since the upper left part is the first part where the current enters, it is coated considerably thicker than the other zone parts. With these changes in the hanger head, a significant difference was observed in plating thickness measurements. Another object of the invention is to provide a curved hanger structure instead of the prior art flat hanger application. Thickness differences were observed after simulating the flat suspension in the plating analysis program and two curved surfaces were designed to eliminate these differences. With this design, the distances of the parts to the anode were modified. In this way, parts can be coated more homogeneously than flat hangers. Another object of the invention is to provide less anode consumption. Another object of the invention is to provide energy saving by achieving desired thickness in a shorter period of time.

In order to fulfill the above-described objects, a plating hanger which is used to ensure homogeneous plating of the materials to be coated by the immersion method and which has at least one hanger frame, and hanger body having part connections holding the materials to be coated thereon, characterized in that the lengths of the part connections on which the material to be coated in low current zones of said plating hanger are attached, are kept long and thereby approximated to the anode, and the lengths of the part connections on which the material to be coated in high current zones are attached are kept short and kept away from the anode. In order to realize all the advantages mentioned above and to be understood from the following detailed description, the present invention provides many advantages due to said features. The structural and characteristic features and all advantages of the invention will become more apparent from the following figures and the detailed description written with reference to these figures, therefore the evaluation should be made with regard to these figures and their detailed description.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows the figurative representation of the plating density in use of the old-type hanger head.

FIG. 2 shows the output of the simulation program of the plating density in use of the hanger head according to the invention.

FIG. 3 shows a perspective view of the plating hanger according to the invention.

FIG. 4 shows a front view of the plating hanger according to the invention.

FIG. 5 shows a side view of the plating hanger according to the invention.

REFERENCE NUMBERS

10. Plating hanger

11. Hanger body

12. Hanger frame

13. Busbar

14. Hanger head

-   -   14.1 Hanger head busbar connecting terminal     -   14.2 Hunger head frame connecting body         -   14.2.1. Long edge         -   14.2.2. Short edge

15. Material to be coated (part)

16. Part (material to be coated) connecting terminal

17. Part connection

CD. Current direction

HPD. High plating density

LPD. Low plating density

DETAILED DESCRIPTION OF THE EMBODIMENTS

In this detailed description, all the technical features and structure of the plating hanger (10), which is developed to ensure the chrome plating of the materials to be coated (15) by chrome in a homogeneous way by the immersion method, will be detailed. FIGS. 3, 4 and 5 show views of the plating hanger (10) according to the invention. In the plating process, the materials to be coated (15) in the central region of the plating hanger (10) are less coated because they remain in the low current zone, whereas the edge regions have more plating thickness because they remain in the high current zone. The high current and low current zones are equalized by changing the distances of the part connections (17), which hold the materials to be coated (15) on the plating hanger (10), to the anode. Accordingly, the distance and angle of the part connecting ends (17), which hold the materials to be coated (15), to the hanger body (11) are changed whereby the distances of the materials to be coated (15) to the anode are changed.

In this way, the materials to be coated (15) in the low current zones of the plating hanger (10) are brought closer to the anode, and the materials to be coated (15) in the high current zones thereof are kept away from the anode whereby it is obtained a more homogeneous plating. This is achieved by changing the length of the part connections (17). The distances of the part connecting terminals (16) to said hanger body (11) is changed by which part connections (17) on the sides are selected shorter and those on the middle part are selected longer such as to form a convex form. Thus, the homogeneous plating is obtained by changing the distance of the material to be coated (15) to the anode according to the current density of said material to be coated (15). The views of FIGS. 3 and 5 illustrate the selected lengths of said part connections (17). The homogeneous plating obtained by said curved (convex) form made on both surfaces of the plating hanger (10) according to the invention is fixed by all experimental data. In a preferred embodiment of the present invention, the hanger body (11) within the hanger frame (12), on which the materials to be coated (15) are hanged, is monolithic and filled with conductive plate. Thus, the current flowing to the materials to be coated (15) on the plating hanger (10) is distributed homogeneously and the plating thickness on the materials to be coated (15) is homogeneous.

In the plating hanger of the present invention, the hanger head (14) which provides the current passage by attaching the plating hanger (10) to the busbar (13) is designed differently from the prior art applications. The result obtained by said hanger head (14) will be more clearly understood by examining the views of FIGS. 1 and 2. FIG. 1 shows the output of the simulation program of the plating density in use of the old-type hanger head. FIG. 2 shows the output of the simulation program of the plating density in use of the hanger head (14) pertaining to the plating hanger (10) according to the invention. In the former embodiment shown in FIG. 1, the outer frame of the hanger constitutes the high current zone, even further since the upper left part is the first part that the current enters, it is coated considerably thicker than the parts in the other zone. More homogeneous plating is obtained when the hanger head (14) of the plating hanger (10) according to the invention (see FIG. 2) is being used. The hanger head busbar connecting terminal (14.1) is designed in U shape and determines the direction of current. Again, the hunger head frame connecting body (14.2) has two long edges (14.2.1) extending at a certain angle towards the right and left upper corners of said hanger frame (12) and short edges (14.2.2) extending towards said hanger frame (12) such as to be in a parallel from the middle of both long edges (14.2.1) to the other edge (14.2.1) in order to distribute the current to the hanger frame (12) at equal density. With this developed form, the materials to be coated (15) in the hanger corner/edge region is prevented to take excessive current and thereby to be coated thin and burned. The plating hanger (10) according to the invention may have different dimensions in alternative areas of application. Therefore, dimensional changes have not been emphasized in the narratives. 

What is claimed is:
 1. A plating hanger for a homogeneous plating of materials to be coated by an immersion method comprising at least one hanger frame, and a hanger body having part connections holding the materials to be coated on the plating hanger, wherein the material to be coated in low current zones of the plating hanger are attached on a first part connections of the part connections, and lengths of the first part connections are kept long and thereby approximated to an anode, and the material to be coated in high current zones are attached on a second part connections of the part connections, and lengths of the second part connections are kept short and kept away from the anode.
 2. The plating hanger according to claim 1, wherein both sides of the plating hanger have a convex form from edge parts of the plating hanger towards middle parts of the plating hanger.
 3. The plating hanger according to claim 1, wherein the hanger body is within the at least one hanger frame the materials to be coated are hanged on the at least one hanger frame, and the hanger body is monolithic and filled with a conductive plate.
 4. The plating hanger according to claim 1, further comprising a hanger head, wherein the hanger head enables to be attached to a busbar and determines a direction and a density of a current.
 5. The plating hanger according to claim 4, wherein the hanger head comprises at least one hanger head busbar connecting terminal designed in a U-shape to determine the direction of the current.
 6. The plating hanger according to claim 4, wherein the hanger head comprises a hunger head frame connecting body to distribute the current on the at least one hanger frame at an equal density.
 7. The plating hanger according to claim 6, wherein the hunger head frame connecting body has two long edges extending at a certain angle towards right and left upper corners of the at least one hanger frame and short edges extending towards the at least one hanger frame such as to be in a parallel from a middle of each of the two long edges (14.2.1) to an other edge to distribute the current to the at least one hanger frame at the equal density. 